Sonance Outdoor series impendence

4.1 PATIO system:

1. The subwoofer is 8 ohms up to crossover point

2. The satellites are 16ohms each down to crossover point, so two in parallel would be 8 ohms

So on the full frequency spectrum, each channel is approx 8 ohms

8.2 PATIO system:

1. The subwoofer is 8 ohms up to crossover point - so two in parallel would be 4 ohms

2. The satellites are 16ohms each down to crossover point, so four in parallel would be 4 ohms

So on the full frequency spectrum, each channel is 4 ohms, depending on frequency

8.1 GARDEN system:

1. The subwoofer is 8 ohms up to crossover point, 2 subs in parallel would be 4ohms

2. The satellites are 32ohms each down to crossover point, so four in parallel would be 8 ohms

So on the full frequency spectrum, each channel is between 4 and 8 ohms, depending on frequency

16.2 GARDEN system:

1. The subwoofer is 8 ohms up to crossover point, so two in parallel would be 4ohms

2. The satellites are 32ohms each down to crossover point, so four in parallel would be 4 ohms

So on the full frequency spectrum, each channel is 4 ohms.

The general rule is the higher the impedance, the easier it is for the amplifier, but you will need more power to deliver the same volume. The figures quoted above are negligible - you won't easily perceive a difference in volume on any of those combinations. 

If you are using a DSP2-150 amplifier then it uses Hypex UCD class D Amplifier modules which have an absolute minimum impedance (not really recommended) of 1 ohm. Therefore neither of your applications will stress or shorten the lifespan of the amplifier.

The key is to keep the overall impedance above about 3 ohms on most modern amplifiers

Online Impendence checker - https://calculator.academy/speaker-impedance-calculator/